What OS platform are you on?
How is the problem described in this ticket different than the one described in #22989?

In running macOS 10.12.6 (16G29). and this problem is different because the hight is much larger than in #22989 and even when I disable torbutton the size decreases only by 10x to 800x. I tested this on a different Mac than #22989, this Mac is a MacBook Pro (Retina, 13-inch, Early 2015), the other Mac in #22989 was a MacBook 12inch late 2015, and my MacBook Pro is connected to a external display.
Resolution: 1920 x 1080 @ 60 Hz

Tor Browser should not necessarily round your content window dimensions to 1000x600. Rather, what it does and should do is rounding the dimensions to multiples of 200x100. Thus having something like 1000x800 is perfectly fine. Resolving this as a duplicate of #22989 then. If I missed something, please say so and reopen this bug.